Income Per Common Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Numerator (basic and diluted):
Net income	$ 116	$ 149
Less: Allocation to unvested restricted stock awards	1	1
Net income available to common shareholders	$ 115	$ 148
Denominator:
Basic common shares (based upon weighted average) (in shares)	293	310
Add: Stock option dilution (in shares)	1	3
Diluted common shares (in shares)	294	313

Amount after tax of income (loss) from continuing operations attributable to the parent.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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